1. Field of the Invention
This invention relates to millimeter wave (MMW), and more particularly, to a multimode millimeter-wave frequency divider circuit with multiple presettable frequency dividing modes which is designed for use with MMW-based circuit systems, such as PLL (phase-locked loop) circuit systems, for providing a multimode frequency dividing function.
2. Description of Related Art
With the advent of wireless digital communication technologies, such as wireless networking, mobile phones, GPS (Global Positioning System), to name just a few, the design and manufacture of MMW (millimeter wave) signal processing circuitry that can handle analog and digital signals within the gigahertz range is in high demand in the electronics industry. Presently, the demand for high-speed MMW signal processing circuitry has advanced to the range from 60 GHz to 77 GHz (gigahertz).
In the design of MMW circuitry, frequency dividers are an essential component used for down-converting an input signal of a high frequency into an output signal of a lower frequency. For high performance purpose, the design of MMW frequency dividers typically requires the capability of frequency locking across a very broad bandwidth. In addition, since most of MMW circuits are to be utilized on portable electronic devices such as mobile phones, the MMW circuit design also requires the capability of low power consumption and compactness in size. In application, frequency dividers are typically integrated to PLL (phase-locked loop) circuitry for synthesis of fixed-frequency signals. Presently, mobile communication systems are operating at the MMW frequencies of 38 GHz, 60 GHz, and 77 GHz. For this sake, the design of MMW IC chips requires the integration of PLL circuitry capable of handing the 38 GHz, 60 GHz, and 77 GHz frequencies.
Presently, one approach to provide multiple-frequency processing capability in one IC chip is to employ three separate PLL circuits respectively used for synthesis of the 38 GHz, 60 GHz, and 77 GHz frequencies. This approach, however, has the drawbacks of requiring large circuit layout space and large power consumption.